Polyesters having increased whiteness

ABSTRACT

LINEAR SYNTHETIC POLYESTERS HAVING INCREASED WHITENESS, THE IMPROVEMENT IN WHITENESS BEING OBTAINED BY INCOPORATION INTO THE POLYESTERS OF A MINOR AMOUNT OF A DIFUNCTIONAL COMPOUND SELECTED FROM THE GROUP CONSISTING OF 1,3-BIS(2-HYDROXYETHOXY)BENZENE, 3-(2-HYDROXYETHOXY) PHENOL, LOWER ALKYL ESTERS OF ADIPIC ACID, LOWER ALKYL ESTERS OF SUBERIC ACID, LOWER ALKYL ESTERS OF AZELAIC ACID, AND LOWER ALKYL ESTERS OF SEBACIC ACID, WITH 1,3-BIS(2-HYDROXYETHOXY)BENZENE, BIS(2-HYDROXYETHYL) AZELATE, AND DIMETHYL AZELATE BEING PREFERRED. THE POLYESTERS MAY BE PREPARED VIA EITHER DIRECT ESTERIFICATION OR ESTER INTERCHANGE. WHEN ESTER INTERCHANGE IS EMPLOYED THE ESTER INTERCHANGE CATALYST IS SELECTED FROM THE GROUP CONSISTING OF SALTS OF TRANSITIONS METALS IN GROUPS II-B, VII-B, AND VIII OF PERIODS 4 AND 5 OR THE PERIODIC TABLE OF THE ELEMENTS, WITH SALTS OF MANGANESE AND COBALT BEING PREFERRED. WHITENESS IMPROVEMENTS ARE IN THE RANGE FROM 6 TO 41 PERCENT RELATIVE TO THE UNMODIFIED POLYESTERS.

United States Patent Ofice 3,697,479 Patented Oct. 10, 1972 ABSTRACT OFTHE DISCLOSURE Linear synthetic polyesters having increased whiteness,the improvement in whiteness being obtained by incorporation into thepolyesters of a minor amount of a difunctional compound selected fromthe group consisting of l,3-bis(2-hydroxyethoxy)benzene, 3-(2hydroxyethoxy) phenol, lower alkyl esters of adipic acid, lower alkylesters of suberic acid, lower alkyl esters of azelaic acid, and loweralkyl esters of sebacic acid, with l,3-bis(2-hydroxyethoxy)benzene,bis(2-hydroxyethyl) azelate, and dimethyl azelate being preferred. Thepolyesters may be prepared via either direct esterification or esterinterchange. When ester interchange is employed the ester interchangecatalyst is selected from the group consisting of salts of transitionmetals in groups II-B, VII-B, and VIII of periods 4 and 5 of theperiodic table of the elements, with salts of manganese and cobalt beingpreferred. Whiteness improvements are in the range from 6 to 41 percentrelative to the unmodified polyesters.

BACKGROUND OF THE INVENTION This invention relates to filmandfiber-forming linear synthetic polyesters. More particularly, thisinvention is directed to filmand fiber-forming linear syntheticpolyesters having increased whiteness.

The utility and commercial acceptance of linear synthetic polyesters,particularly poly(ethylene terephthalate) are well known. There havebeen, however, numerous attempts to provide modified polyesters, andmodified poly (ethylene terephthalate) in particular, with improvedproperties to further enhance the commercial acceptance of said linearsynthetic polyesters. Representative of said improved properties areimproved thermal stability, substantial elimination of diglycol,improved receptivity to dyestuffs of various types and improvedwhiteness.

Polymer whiteness is especially important when said linear syntheticpolyesters are converted into filaments and fibers for fabric andapparel end uses. For these end uses, white filaments and fibers arehighly desirable for both aesthetic and practical considerations.Whether as fabrics or apparel, increased yarn whiteness results in Whitegoods having greater consumer appeal. This factor is sufficientlyimportant to warrant a separate bleaching step for fabrics made fromyarns which are off-white. Even if the yarn, as fabric, is to be dyed, ahigh degree of whiteness is desirable since off-white yarns result indyed goods which are off-color. Thus, white yarns greatly simplifyquality control and color matching of dyed goods and the aforementionedbleaching step is therefore required for yarns which are off-white incolor. Furthermore, off-white fibers give a reeded out orunderconstructed appearance to polyester or polyester/cotton fabrics.

By polymer (or fabric) whiteness is meant the degree of whiteness ofsaid polymer (or fabric) when compared with a ceramic tile standard. Inpractice, this comparison is accomplished by means of an instrument(such as a Hunterlab Model D-40 Reflectometer for Whiteness) whichmeasures the reflectance of the sample and standard. From the dataobtained, a quantitative expression is secured which characterizes thedegree of whiteness of the sample.

A more detailed description of the procedure may be found elsewhere inthis specification. It is preferred that the products of this inventionhave a whiteness rating of at least 70 as measured on a Hunterlab ModelD-40 Reflectometer for Whiteness as described elsewhere in thisspecification.

In the past various methods have been recommended to improve thewhiteness of linear synthetic polyesters, Prominent among these methodsis the incorporation of additives, including monomers capable ofcopolymerization, into said polyesters. Frequently, however, ifwhiteness Were improved, another property such as lightfastness wasdetrimentally alfected.

SUMMARY OF THE INVENTION It is therefore an object of the presentinvention to provide modified polyester compositions which, whenconverted into fibers and fabrics, exhibit increased whiteness withoutlosing the desirable properties of the unmodified polyesters.

Another object of the invention is to provide a process for thepreparation of the modified polyester compositions exhibiting increasedwhiteness.

These and other objects and advantages of the present invention aredescribed :more fully in the specification and claims which follow.

It has now been found, quite unexpectedly, that incorporation intolinear synthetic polyesters of a minor amount of a difunctional compoundselected from the group consisting of 1,3-bis(Z-hydroxyethoxy)benzene,3-(2-hydroxyethoxy)phenol, lower alkyl esters of adipic acid, loweralkyl esters of suberic acid, lower alkyl esters of azelaic acid andlower alkyl esters of sebacic acid results in an increase in polymerwhiteness in the range from 6 to 41 percent, relative to the unmodifiedpolyesters. By the term lower alkyl is meant aliphatic radicals of fromabout 1 to about 6 carbon atoms. Preferably, the compound is selectedfrom the group consisting of 1,3-bis(2-hydroxyethoxy)benzene,bis(2-hydroxyethyl) azelate and dimethyl azelate. By incorporation of aminor amount of the compounds of the present invention is meant lessthan about 5 weight percent, based upon the weight of dicanboxylic acidor its dialkyl ester; the preferred level of incorporation is 3 weightpercent. In general, the compounds of the present invention are addedprior to substantial polycondensation. The polyesters may be prepared byeither direct esterification or ester interchange. When esterinterchange is employed, the ester interchange catalyst is selected fromthe group consisting of salts of transition metals in groups II-B,VII-B, and VIII of periods 4 and 5 of the periodic table of theelements, with salts of manganese and cobalt being preferred.

DETAILED DESCRIPTION OF THE INVENTION The term linear syntheticpolyester as used herein, includes as a preferred class, polyestersbased upon terephthalic acid or its dialkyl ester and as a morepreferred class, polyesters prepared from terephthalic acid or itsdialkyl ester and a polymethylene glycol having the formula:

HO CH OH wherein n is an integer from 2 to about 8. In this morepreferred class, the most preferred polyester, poly(ethyleneterephthalate), is obtained when n is 2. While both directesterification of a dicarboxylic acid with a diol followed bypolycondensation, and ester interchange of a dicarboxylic acid dialkylester with a diol followed by polycondensation are within the scope ofthis invention, the latter process for the preparation of linearsynthetic polyesters is preferred.

In the preferred process, ester interchange of a di-- carboxylic aciddialkyl ester with a diol followed by polycondensation, an esterinterchange catalyst usually is required in order to permit completionof the ester interchange step within a practical length of time.Unexpectedly, it has been found that the ester interchange catalystemployed may render the compounds of the present invention ineffectivein increasing the whiteness of linear synthetic polyesters. Accordingly,the ester interchange catalyst is selected from the group consisting ofsalts of transition metals in groups II-B, VII-B, and VIII of periods 4and 5 of the periodic table, of the elements (Robert C. Weast, Editor,Handbook of Chemistry and Physics, 49th Edition, The Chemical RubberCo., Cleveland, Ohio, 1968, p. B-3), such as manganese acetate, ferricacetate, ferric stearate, ferrous carbonate, cobalt acetate, cobaltformate, lead acetate, lead oxide, zinc thioantimonate, zinc acetate,zinc cyanide, cadmium acetate, and cadmium cyanide. Preferably, theester interchange catalyst is selected from the group consisting ofsalts of manganese and cobalt, and particularly manganese and cobaltsalts of aliphatic monocarboxylic acids having up to about 6 carbonatoms.

In addition to the reaction components, the compounds of the presentinvention as heretofore described, and an ester interchange catalyst,various other materials may be present. For example, such polymerizationcatalysts as antimony trioxide, antimonic acid, germanium dioxide,stannous oxalate, organo-titanium compounds, and the like usually willbe present. Preferably, the polymerization catalyst will be selectedfrom the group consisting of antimony trioxide and antimonic acid.Furthermore, color inhibitors, such as alkyl or aryl phosphate esters,alkyl or aryl phosphite esters, and the like may be used. In addition,pigments, delustrants such as titanium dioxide, and other additives maybe present. It is preferred that the linear synthetic polyesters of thepresent invention be delustered in order to realize the greatest benefitfrom the present invention.

The fibers or filaments in continuous or stable form produced inaccordance'with the present invention are suitable for the usual textileapplications. They may be employed in the knitting or weaving of alltypes of products as well as in the production of non-woven, felt-likeproducts produced by known methods. The physical properties of themodified fibers or filaments closely parallel those of their relatednon-modified polyester yarns. The modified yarns ditfer, however, inthat they have increased whiteness.

Without intending to limit it in any manner, the following. exampleswill serve to illustrate the invention.

Example 1 Preparation of put-polymer.A five-gallon jacketed autoclave,heated by means of a Dowtherm vapor system (heat transfer mediummanufactured by Dow Chemical Co., Midland, Mich.) and fitted with anagitator and condenser, is charged with 30.0 pounds of dimethylterephthalate, 21.6 pounds of ethylene glycol and 5.44 grams of cobaltacetate. The mixture is heated to reflux at atmospheric pressure. Thetemperature of the mixture is about 187 C. when methanol begins todistill. Methanol distillation is complete after about 2.5 hours; batchtemperature has. increased to about 220 C. The mixture is extruded,cooled, ground, and packaged and referred to hereinafter as cobaltprepolymer.

Preparation of polymer.A two-liter, stainless steel, electrically-heatedautoclave, fitted with agitator, condenser, thermocouple, and means foroperating under reduced pressure, is charged with 750 grams of cobaltpre-polymer, 2.0 grams of titanium dioxide, 0.54 gramof a 50% solutionvof trimethyl phosphite in ethylene glycol, 0.23 gram of antimonic acid,and 17.1 grams of bis(2-hydroxyethyl) azelate. The autoclave'is purgedwith nitrogen and heated to about 230 C. before beginning vacuumletdown. At the completion of vacuum let-down, which requires about 75minutes, the batch is polymerized at 280 C. and 0.7 millimeter Hgpressure for 70 minutes. The batch is extruded into water. The resultantpolymer is found to have an intrinsic viscosity of 0.562 deciliter pergram and a melting point of 255 C. as determined by differential thermalanalysis.

As used herein, intrinsic viscosity is a measure of the degree ofpolymerization of the polyester and may be defined as:

Limit Z as C approaches zero where n is the viscosity of a dilutesolution of the polyester in o-chlorophenol, no is the viscosity of thepure solvent measured in the same units and at the same temperature as 1and C is the concentration in grams of polyester per milliliters ofsolvent. Thus, intrinsic viscosity has the units, deciliters per gram.

The melting points of the polymers of this example and the exampleswhich follow are readily determined by differential thermal analysis(DTA), a well known and widely recognized technique. The apparatus usedis ,a du Pont Model 900 Differential Thermal Analyzer. The meltingpoints are determined using a glass macro sampling tube with a ceramicsleeve under a nitrogen flow of one liter per minute and with a heat-uprate of 20 C. per minute; the reference is glass beads.

The polymer is converted into 70 denier filament yarn having 36filaments and knitted into a hoseleg. The fabric is found to have aHunter D-40 Whiteness Rating of 51.2.

The Hunter D-40 Whiteness Rating, as used herein, is the whitenessrating as determined with a Hunterlab Model D-40 Reflectometer forWhiteness (manufactured by Hunter Associates Laboratory, Inc., Fairfax,Va.), a reflectometer specifically designed for whiteness measurements.The illuminator is International Commission on Illumination (C. I.E.)Source C, and a rotating ultraviolet filter is located between theilluminator and the specimen. The ultraviolet wavelengths can either'befiltered out or allowed to pass on to the specimen. The instrument iscalibrated with ceramic tile standards. Readings of reflectances aretaken by nulling a galvanometer with a calibrated potentiometer which isso scaled that percent reflectances are read directly from theinstrument. The quantities measured are: (1) green reflectance excludingincident ultraviolet light, denoted as GCE); (2) blue reflectanceexcluding incident ultrawiolet light, denoted as B(E); and (3) bluereflectance including incident ultraviolet 'light, denoted as B(I). Thequantities calculated are: (1) percent blue reflectance due tofluorescent materials, such as optical brighteners, in or on thespecimen, calculated according to Equation 1; and the Whiteness ofpercent BR=B(I) -B (E) (1) the specimen, calculated according toEquation 2. A more detailed discussion of the theory and function of theinstrument, including the rationale behind the preferred use of Equation2, may be found in the article, New Refiectometer and Its Use forWhiteness Measurement, by

Richard S. Hunter, in the Journal of Optical Society of America, volume50, number 1 (January 1960), pp. 44 48.

As a control, the polymerization of Example 1 is repeated, using cobaltpre-polymer, except that the bis(2- hydroxyethyl) azelate is omitted.The resultant polymer has an intrinsic viscosity of 0.640 deciliter pergram and a DTA melting point of 261 C. The polymer is converted into70-denier filament yarn having 36 filaments and knitted into a hoseleg.The fabric is found to have a Hunter Whiteness Rating of 44.6.

Since the whiteness rating of any given sample is meaningful only uponcomparison with a control, it is helpful to also express the whitenessof any given sample in Example 2 Using cobalt per-polymer, thepolymerization of Example l is repeated, except that thebis(Z-hydroxyethyl) azelate is replaced with an equal amount of3-(2-hydroxyethoxy) phenol. Results similar to those of Example 1 areobtained upon comparing yarn prepared from the resultant polymer withthe control of Example 1.

Example 3 Using cobalt pre-po'lymer, the polymerization of Example 1 isrepeated, except that the bis(Z-hydroxyethyl) azelate is replaced withan equal amount of dimethyl adipate. Results similar to those of Example1 are obtained upon comparing yarn prepared from the resultant polymerwith the control of Example 1.

Example 4 Using cobalt pre-polymer, the polymerization of Example 1 isrepeated, except that the =bis(2-hydroxyethyl) azelate is replaced withan equal amount of dimethyl sebacate. Results similar to those ofExample 1 are obtained upon comparing yarn prepared from the resultantpolymer with the control of Example 1.

Example 5 A two-liter, stainless-steel, electrically heated autoclave,fitted with agitator, thermocouple, condenser with proportional take-offhead, and means for operating under reduced pressure, is charged with 6grams of dimethyl terephthalate, 432 grams of ethylene glycol, and 0.21gram of cobalt acetate. The autoclave is purged with nitrogen and heatapplied. Methanol distillation begins when the batch temperature is 175C. Methanol distillation is continued, initially at 0% take-01f andfinally at 20% take-01f, for a period of about five hours at the end ofwhich time the batch temperature isabout 220 C. To insure the completedistillation of methanol, distillate taJke-olf is increased to 90% andethylene glycol distilled for about 20 minutes; the batch temperature isnow 230 C. The condenser assembly is removed from the autoclave which ischarged with 2.1 grams of titanium dioxide, 0.24 gram of antimonic acid,0.30 gram of a 50% solution of trimethyl phosphite in ethylene glycol,and 18.0 grams of 1,3-bis(2-hydroxyethoxy)benzene. The autoclave isfitted with a concentrator (concentrating condenser) 'with vacuumadapter and the autoclave purged with nitrogen. Vacuum let-down isinitiated and requires about 45 minutes for completion. The batch ispolymerized at 280 C. and 0.6 millimeter Hg for 2 hours. The resultingpolymer is extruded into water and has an intrinsic viscosity of 0.593deciliter per gram and a DTA melting point of 252 C.

The polymer is converted into 70/36 filament yarn and knitted into ahoseleg. The fabric is found to have a Hunter Whiteness 'Rating of 72.1.

To prepare a control, the procedure of Example 3 is repeated, exceptthat the 1,3-bis(2-hydroxyethoxy)benzone is omitted. The resultantpolymer has an intrinsic viscosity of 0.564 and a DTA melting point of258 C. The polymer is converted into 70/ 36 filament yarn which isknitted into a hoseleg. The fabric is found to have a Hunter WhitenessRating of 67.5. Thus, the polymer of Example 3 is 7% whiter than thecontrol polymer which lacks l,3-bis(2-hydroxyethoxy) benzene.

Example 6 The procedure of Example 5 is repeated, except that the1,3-bis(2-hydroxyethoxy)benzene is replaced with an equal amount ofbis(Z-hydroxyethyl) azelate. The resultant polymer is found to have anintrinsic viscosity of 0.581 deciliters per gram and a DTA melting pointof 256 C.

The polymer is converted into 70/ 36 filament yarn and knitted into ahoseleg which is found to have a Hunter Whiteness Rating of 71.4. Thus,the polymer of this example shows an improvement in whiteness of 6% whencompared with polymer lacking the bis(Z-hydroxyethyl) azelate: thecontrol of Example 5 which has a Hunter Whiteness Rating of 67.5.

Example 7 The procedure of Example 5 is repeated, except that the 1,3-bis(2-hydroxyethoxy) benzene is replaced with an equal amount ofdimethyl azelate. The resultant polymer has an intrinsic viscosity of0.529 deciliter per gram and a DTA melting point of 254 C.

The polymer is converted into 70/ 36 filament yarn and knitted into ahoseleg having a Hunter Whiteness Rating of 84.0, an improvement of 24%over the control of Example 5 which lacks the dimethyl azelate and has aHunter Whiteness Rating of 67.5.

Example 8 The procedure of Example 5 is repeated, except that the cobaltacetate ester interchange catalyst is replaced with an equal amount ofmanganese acetate. The resultant polymer has an intrinsic viscosity of0.574 and a DTA melting point of 244 C.

The polymer is converted into 70/ 36 filament yarn and knitted into ahoseleg. The fabric is found to have a Hunter Whiteness Rating of 56.9.

As a control, the procedure of Example 6 is repeated except that the1,3-bis(2hydroxyethoxy)benzene is omitted. The resultant polymer has anintrinsic viscosity of 0.564 deciliter per gram and a DTA melting pointof 257 C. The polymer is converted into 70/36 filament yarn which isknitted into a hoseleg having a Hunter Whiteness Rating of 47.6. Thus,the incorporation of 1,3- bis(2-hydroxyethoxy)benzene into polyesterresults in an improvement in whiteness of 20%.

Example 9 The procedure of Example 6 is repeated except that the cobaltacetate ester interchange catalyst is replaced With an equal amount ofmanganese acetate. The resultant polymer has an intrinsic viscosity of0.644 and a DTA melting point of 252 C.

The polymer is converted into 70/ 36 filament yarn and knitted into ahoseleg having a Hunter Whiteness Rating of 67.1, an improvement of 41%over the control of Example 8 which lacks the bis(Z-hydroxyethyl)azelate and has a Hunter Whiteness Rating of 47.6.

Example 10 The procedure of Example 7 is repeated except that theco'balt acetate ester interchange catalyst is replaced with an equalamount of manganese acetate. The resultant polymer has an intrinsicviscosity of 0.565 deciliter per gram and a DTA melting point of 256 C.

The polymer is converted into 70/ 36 filament yarn and knitted into ahoseleg. The fabric is found to have a Hunter Whiteness Rating of 65.0,an improvement of 37 over the control of Example 8 which lacks thedimethyl azelate and has a Hunter Whiteness Rating of 47.6.

As already indicated, some ester interchange catalysts have adeleterious efiect upon the usefulness of the compounds of the presentinvention in increasing the whiteness of linear synthetic polyesters.This effect is illustrated by Examples 11, 12, and 13.

Example 11 The procedure of Example is repeated, except that the cobaltacetate ester interchange catalyst is replaced with an equal amount ofmagnesium carbonate. The re- 8 Example :14-

The hoseleg samples of Examples 8-13, inclusive, are bleached andheat-set and Hunter Whiteness Ratings obsultant polymer has an intrinsicviscosity f 0.554 deci 5 tained for the treated fabrics. The results aresummarized liter per gram and a DTA melting point of 248 C. in TableTABLE I Percent improve- Hoseleg sample Additive El. cat. Rating mentControl of Example 8 None. Manganese acetate... 75.2 Example:

8 1,3-bis (2-hydroxy ethoxy)benzene do. 83. 1 11Bis(Zhydroxyethyl)azelate..- e d0- 109. 1 45 10...-.- Dimethyl azelatedo 91. 2 21 ggangollgf Example 11-....- None Magnesium carbonate- 105.411% 1,3-bis(2-hydroxyethoxy)benzene do 91.5 --13 12.. Bis(2hydroxyethyl) axelate -do 94.0 -11 l3. Dimethyl azelate -d0. 49. 4 53The polymer is converted into 70/36 filament yarn and An inspection ofthe data in Table I shows that the knitted into a hoseleg having aHunter Whiteness Rating bleaching and heat-setting steps in general didnot change of 54.8. the relative whitenesses of the samples, althoughthe To .preparea control, the procedure of Example I l is bleaching stepincreased the whiteness of each sample repeated except that the1,3-bis(2-hydroxyethoxy)benzene relative to untreated fabric. isomitted. The resultant polymer has an intrinsic vis- Since the productsof the present invention are suitable cosity of 0.518 deciliter per gramand a DTA melting for fabric and apparel end uses wherein dyed orcolored point of 261 C. The polymerv is converted into 70/3'6 articlesare desired, the properties of the dyed articles filament yarn which isknitted into a hoseleg; the fabric is made from the products of thepresent invention are imfound to have a Hunter Whiteness Rating of 65.0.Thus, portant. The most significant property of a dyed article themagnesium-catalyzed polymer containing 1,3-bis(2- is its fastness tolight. The lightfastness of a textile article hydroxye-thoxy)-benzene is16% less white than the conusually is determined by means of theFade-Ometer trol polymer lacking 1,3-bis(2-hydroxyethoxy)benzene.(manufactured by Atlas Electric Devices Company, Chi- Example 12 cago,111.), a self-contained, electrically-operated device for theaccelerated testing of the stability of dyed articles The ProcedureOfEXample 6 is repeated, xcept that to daylight. Basically, the devicesimply exposes the samthe cobalt acetate ester interchange catalyst isreplaced ple to light produced by a carbon are for any given with anequal amount of magnesium carbonate. The relength of time. The exposedsample then is rated visually sultant polymer has an intrinsic ViSCOSitY0f 0.635 deciliter on a scale from 1 to 5, wherein 1 indicates complet 1P gram and DTA melting Point Of of color and 5 indicates no changev incolor. It should be The polymer is converted into 70/36 filament yarn amentioned that the data obtained using a particular apknitted into ahoseleg. The fabric is found to have a paratus may not be compared withdata obtained using Hunter Whiteness Rating of 55.0, a decrease inwhiteness a second, similar apparatus since the intensity of the lightof 15% when pa with the 6011301 of Example source varies from apparatusto apparatus. In general, a which leeks the y y yl) azelate and has arating of 3 or above after 20 hours indicates satisfactory HunterWhiteness Rating of lightfastness for the usual textile end uses, carpetend Example 13 uses excluded. That the products of the present inventionhave satisfactory lightfastness properties when dyed is The procedure ofExample 7 is repeated, except that Shown by Example 5 the cobalt acetateester interchange catalyst is replaced with an equal amount of magnesiumcarbonate. The re- Example 15 sultant polymer has an intrinsic viscosityof 0.606 and a DTA melting point of 257 C.

The polymer is converted into 70/36 filament yarn and The hse.1egS ofExamples 5-13 i Separately knitted into a hoseleg. The fabric is foundto have a aredqyed wlth Eastmfm Blue F a dlsperse Hunter WhitenessRating of 44.0, a decrease in whiteness cor mg to the folloivmgprocedure The dyebath conslsts of 33% when compared with the control ofExample 11 aqueous solutlon. of 1% Eastman. Blue GBLF which lacks thedimethyl azelate and has a Hunter Whitetammg 2 grflms Per mer monosodmmP Hess Rating of grams per liter of Carrohd ELl C, a carrier of the bi-The ultimate utility of any process for improving poly- Phenyl type andg of TanaPon X40, a mer whiteness (and hence the whiteness of productsmade Surfactant; The fabrfc 15 treated m the dyebeth 1 hour from suchimproved polymer) depends upon the permaat. the b011, then used, scouredand The y nence of the improvement in whiteness obtained. That thefabric then is exposed 20 hours in the fl e effects obtained by the useof the compounds of thi and the exposed fabric rated visually. Theresults are invention are permanent is illustrated by Example 14.summarized in Table II.

TABLE II Hoseleg sample Additive El. catalyst Rating A. Heat-set priorto dyeing Control of N one Cobalt acetate 3 Example 5. Example 5...-1,3-bis(2-hydroxyethoxy) .do 3-4 benzene.

Example 6.-.. Bis(2-hydroxyethy1)azelate ..do 3-4 Example 7.... Dimethylazelate ..do 34+ B. Heat-set after dyeing Control of None Cobaltacetate. 3-4

Example 6. Example 5.-.- 1,3-bis(2-hydroxyethoxy) -do 3-4 enzene.

Example 6...- Bis(2-hydroxyethyl)aze1ate ..;...-do 4 Example 7..-.Dimethyl azelate ..do 4

C. Bleached and heat-set prior to dyeing Control of None ManganeseExample 8. acetate. Example 8.... 1,3-bis(2-hyd.roxyethoxy) ...-.do 3+enzene. Example 9-... Bis(Z-hydroxyethybazelate- ....do 3 Example 10--.Dimethyl azelate -...do. 4 Control of None Magnesium 3+ Examplecarbonate. 11. Example 11... 1,3-bis(2-hydroxyethoxy) do 3+ benzene.Example 12--- Bis(2-hyd.roxyethyl)azelate ..do 34 Example 13..- Dimethylazelate .-do 3 Thus, the products of the present invention allow thepreparation of dyed fabrics having lightfastness properties equal to orsuperior than the lightfastness properties of dyed fabrics made fromunmodified polymer. This effect is independent of the effect of thecompounds of the present invention upon the whiteness properties of thepolymers.

It is well known in the art that polymer color is intimately related tocatalyst residues, although the exact nature of said catalyst residuesis not always known. For example, salts of lead tend to give polymershaving a yellow color whereas salts of germanium tend to give polymerswhich are relatively white. Without wishing to be bound by theory, it isbelieved that the ester interchange catalyst interacts with thecompounds of the present invention to either reduce the amount ofcolored catalyst residues or to alter the nature of such residues,thereby reducing the amount of coloration produced in the polymer.Accordingly, it is preferable to add the compounds of the presentinvention prior to polycondensation so that the desired color-reducinginteraction may occur before the stringent conditions ofpolycondensation are imposed upon the system. Loss of the compounds ofthe present invention from the system during polycondensation generallyis not a problem since the glycol component of the polyester usuallywill have a lower boiling point than the compounds of the presentinvention. Of course, addition of the compounds of the present inventionat the beginning of the ester interchange reaction is possible andwithin the scope of the present invention.

Having thus disclosed the invention, what is claimed is:

1. In a process for producing a linear terephthalate polyester from adialkyl ester of terephthalic acid and a glycol having the formula:

HO (CH OH wherein n is an integer from 2 to about 10, said processcomprising elfecting the ester interchange of said dialkyl ester andsaid glycol in the presence of a catalyst selected from the groupconsisting of salts of transition metals in Groups II-B, VII-B and VIIIof periods 4 and 5 of the periodic table of elements, the improvementcomprising adding to the products of the ester interchange reactionprior to substantial polycondensation up to about 5 weight percent,based upon the amount of terephthalic acid dialkyl ester, of adifunctional compound selected from the group consisting of1,3-bis-(2-hydroxyethoxy) benzene, 3- (Z-hydroxyethoxy) phenol, bis-(2-hydroxyethyl) azelate, alkyl esters of adipic acid, alkyl esters ofsuberic acid, alkyl esters of azelaic acid and alkyl esters of sebacicacid prior to substantial polycondensation, wherein said alkyl groupcontains from 1 to about 6 carbon atoms, said polyester being suitablefor the production of films or filaments and fibers having improvedwhiteness as defined by a Hunter D-40 whiteness Rating as compared withunimproved but otherwise equivalent polyester.

2. The process of claim 1 wherein the difunctional compound added isselected from the group consisting of 1,3 bis(2 hydroxyethoxy)benzene,bis(2-hydr0xyethyl) azelate, and dimethyl azelate.

3. The process of claim 2 wherein the ester interchange catalyst isselected from the group consisting of salts of manganese and cobalt.

4. The process of claim 1 wherein said linear synthetic polyester ispoly(ethylene terephthalate).

References Cited UNITED STATES PATENTS 2,973,339 2/ 1961 Muenster et al.26047 3,341,500 9/ 1967 Schwarz 260- 3,372,148 3/ 1968 Wiener 260-753,403,132 9/1968 Waller 260-47 3,554,976 1/1971 Hull 260-75 2,901,4668/1959 Kibler et a1 260-75 2,998,412 8/ 1961 Fletcher 260-75 3,008,93411/1961 Wielicki et al. 260-75 3,028,366 4/1962 Engle et a1. 260-753,053,810 9/1962 Griehl et al 260-75 3,110,547 12/1963 Emmert 260-75FOREIGN PATENTS 931,241 7/1963 Great Britain. 938,055 9/ 1963 GreatBritain.

MELVIN GOLDSTEIN, Primary Examiner US. Cl. X.R. 5260-75 R

